Putting Mercury In Food Into Perspective: What You Need To Know 

The presence of heavy metals in food is not new. Mercury, like most heavy metals, is naturally occurring and can be detected at trace levels in food. Mercury can, however, accumulate in oceans, lakes, and streams, where it transforms into methylmercury, which can build up in seafood. People are primarily exposed to mercury by eating seafood. Exposure to mercury remains extremely low per the U.S. and global monitoring systems that are in place. Still, overexposure to mercury can cause adverse health effects.   

Adults can safely consume 2 – 3 servings of “Best Choices” fish per week. Pregnant women, breastfeeding mothers, and young children are advised to choose options like salmon or shrimp, in a category identified as “Best Choices” according to U.S. Food and Drug Administration (FDA) and Environmental Protection Agency (EPA) due to their lowest methylmercury content. Ongoing FDA testing and monitoring help reduce risks and ensure seafood safety for consumers.  

To further reduce exposure to mercury and other heavy metals through food as well as promote good health and nutrition, consumers should continue to eat a variety of nutrient-dense foods across and within the main food groups of vegetables, fruits, grains, dairy, and proteins.  

What Is Mercury?

Mercury is a naturally occurring element that can accumulate in oceans, lakes, and streams, where it transforms into methylmercury, which can build up in fish and shellfish.  

How Are Consumers Exposed To Mercury Or Methylmercury?

While consumers can become exposed to mercury in various ways, the primary human exposure is through consuming contaminated fish and seafood. Once in the air, mercury settles into bodies of water where microorganisms convert it into methylmercury, which can accumulate in fish and shellfish. The highest methylmercury concentrations are found in larger fish that eat other smaller fish.  

Low levels of mercury may be present in agricultural foods, depending on natural geographical makeup and proximity to current, past use, or manufacturing of products made with mercury. For example, mercury can be distributed in the environment from volcanic activity, geological weathering, and can be higher in areas where mining and manufacturing occurred. 

How Much Mercury Is Safe?

The U.S. Environmental Protection Agency’s (EPA) reference dose for mercury is 0.045 micrograms (mcg) per pound of body weight daily. For example, a 100-pound person’s safe limit is 4.5 µg/day, while for a 150-pound person, it’s 6.8 µg/day. 

What Health Risks Are Associated With Overexposure To Mercury? 

Most people have trace mercury in their bodies, but typically at levels below those associated with health effects. Overexposure impacts vary across the lifespan: 

• Infants and children: Methylmercury exposure during pregnancy can harm fetal brain and nervous system development, affecting cognition, memory, language, and motor skills. Children are especially vulnerable due to smaller body sizes and rapid growth. 

• Adults: Prolonged or sudden overexposure may cause depression, memory issues, muscle weakness, vision or speech problems, balance issues, and metallic taste. Diagnosis requires medical testing of blood or urine mercury levels.

There is no confirmed link between methylmercury exposure and coronary heart disease or cancer. 

What Is Being Done To Reduce Exposure To Mercury?

The U.S. Food and Drug Administration (FDA) and global regulators set safety limits for heavy metals in food and water. U.S. initiatives like FDA’s Closer To Zero program are actively working to reduce exposure to heavy metals for all ages. The FDA prioritizes ensuring food safety while also promoting the positive effect of nutrient-rich food options.  

Key actions include: 

• Monitoring mercury in food: Programs like the Total Diet Study track nutrient and contaminant levels in foods nationwide to assess exposure and inform interventions. 

• Issuing consumer guidance: In collaboration with the EPA, the FDA issues advice on fish consumption to reduce mercury exposure, particularly for vulnerable populations, such as pregnant or breastfeeding women and young children. Fish are categorized by mercury levels, and recommendations focus on balancing nutritional benefits with safety. 

How Can Consumers Lower Their Mercury Exposure?

Seafood provides important nutrients of public health importance, including protein. Additionally, fish and shellfish are the highest source of omega-3 fatty acids DHA and EPA, which along with choline in seafood, are important for the prenatal period and throughout childhood for brain development. To maximize benefits while minimizing mercury exposure, consumers should choose low-mercury seafood options. 

While mercury is commonly associated with eating fish, it is not found at unsafe levels in all types of fish. The FDA and EPA Guidelines outline “Best Choices” of seafood lower in methylmercury, advice which supports the recommendations of the Dietary Guidelines for Americans: 

• Adults: Eat 2–3 servings (8–12 ounces total) of “Best Choices” fish per week. Options are also provided for “Good Choices” at 1 serving per week. 

• Children: Consume 2 servings per week from the “Best Choices” list with age-appropriate portions: 1 ounce for ages 1–3 years; 2 ounces for ages 4–7 years; 3 ounces for ages 8–10 years; and 4 ounces for ages 11 years and older. 

Visit FDA’s Advice about Eating Fish for specific advice for individuals who are pregnant, breastfeeding, or feeding young children. 

References 

1. How People are Exposed to Mercury, U.S. Environmental Protection Agency, March 15, 2024. Retrieved here on 11/14/2024.  
2. Mercury in Food, U.S. Food and Drug Administration, March 5, 2024. Retrieved here on 11/14/2024. 
3. Technical Information on Development of FDA/EPA Advice about Eating Fish for Those Who Might Become or Are Pregnant or Breastfeeding and Children Ages 1-11 Years, U.S. Food and Drug Administration, June 7, 2024. Retrieved here on 11/14/2024.  
4. Health Effects of Exposure to Mercury, U.S. Environmental Protection Agency, March 15, 2024. Retrieved here on 11/14/2024. 
5. Mozaffarian D. Fish, mercury, selenium and cardiovascular risk: current evidence and unanswered questions. Int J Environ Res Public Health. 2009 Jun;6(6):1894-916. doi: 10.3390/ijerph6061894. 
6. Advice about Eating Fish, U.S. Food and Drug Administration, March 5, 2024. Retrieved here on 11/14/2024. 
7. Questions & Answers from the FDA/EPA Advice about Eating Fish for Those Who Might Become or Are Pregnant or Breastfeeding and Children Ages 1 to 11 Years, U.S. Food and Drug Administration, February 17, 2022, Retrieved here on 11/14/2024.  
8. U.S. Department of Agriculture and U.S. Department of Health and Human Services. Dietary Guidelines for Americans, 2020-2025. 9th Edition.